#!/usr/bin/env bash

target=$1

ask_for_execution() {
    USER_ANSWER="?";
    while [ "${USER_ANSWER}" != "n" ] && [ "${USER_ANSWER}" != "y" ] && [ "${USER_ANSWER}" != "q" ]
    do
        echo -n "Is this the good target ? [y/n/q]"
        read -r -n 1 USER_ANSWER
        echo "";
    done
    if [ "$USER_ANSWER" == "y" ]
    then
        return 0
    elif [ "$USER_ANSWER" == "n" ]
    then
        return 1
    elif [ "$USER_ANSWER" == "q" ]
    then
        exit 0
    else
        exit 0
    fi
}

check_virtual_kernel_filesystems()
{
    echo "call check_virtual_kernel_filesystems"
    if mount |grep -q "udev on ${target}/dev type devtmpfs"        && \
       mount |grep -q "devpts on ${target}/dev/pts type devpts"    && \
       mount |grep -q "proc on ${target}/proc type proc"           && \
       mount |grep -q "sysfs on ${target}/sys type sysfs"          && \
       mount |grep -q "tmpfs on ${target}/run type tmpfs"          && \
       mount |grep -q "tmpfs on ${target}/dev/shm type tmpfs"
    then
        echo "Ok, Filesystems are ready for chroot"
        return 0
    else
        echo "Warning : Not ready for chroot !!!"
        return 1
    fi
}

mount_virtual_kernel_filesystem()
{
  echo "call mount_virtual_kernel_filesystem"
  echo "sudo operation : mount dev sys proc sys run /dev/shm on ${target}"
  sudo /usr/bin/mount -v --bind /dev "${target}/dev" || return 1
  sudo /usr/bin/mount -vt devpts devpts -o gid=5,mode=0620 "${target}/dev/pts" || return 1
  sudo /usr/bin/mount -vt proc proc "${target}/proc" || return 1
  sudo /usr/bin/mount -vt sysfs sysfs "${target}/sys" || return 1
  sudo /usr/bin/mount -vt tmpfs tmpfs "${target}/run" || return 1
  echo "Content of ${target}/dev :"
  ls -l "${target}/dev/"
  echo "Content of ${target}/dev/shm :"
  ls -l "${target}/dev/shm"
  if [ -h "${target}/dev/shm" ]
  then
      echo /usr/bin/install -v -d -m 1777 "${target}$(realpath /dev/shm)" || return 1
      sudo /usr/bin/install -v -d -m 1777 "${target}$(realpath /dev/shm)" || return 1
  else
      echo /usr/bin/mount -vt tmpfs -o nosuid,nodev tmpfs "${target}/dev/shm" || return 1
      sudo /usr/bin/mount -vt tmpfs -o nosuid,nodev tmpfs "${target}/dev/shm" || return 1
  fi
  return 0
}

cat > "${HOME}"/target_chroot.sh <<EOSF
if ! mount |grep -q "proc on ${target}/proc type proc"
then
    echo "chroot is not available at this step"
    exit 1
fi
sudo /usr/sbin/chroot ${target} /usr/bin/env -i \
    HOME=/root                          \
    TERM="${TERM}"                      \
    debian_chroot=" ${target} "           \
    PS1='(chroot ${target}) \u:\w \$ '   \
    PATH=/usr/bin:/usr/sbin             \
    /bin/bash --login
EOSF

cat > "/tmp/$(whoami)_sudo" << EOF
$(whoami) ALL = NOPASSWD: /usr/bin/mount * ${target}*
$(whoami) ALL = NOPASSWD: /usr/sbin/chroot ${target}*
EOF

target_chroot()
{
    echo "call target_chroot $1"
    CHROOTFILE=$1
    sed "1iif [[ ! \"\${UID\}\" -eq 0 ]] && [ ! -e ${CHROOTFILE} ]" -i "${CHROOTFILE}"
    sed "2ithen" -i "${CHROOTFILE}"
    sed "3iecho \"bad chroot\"" -i "${CHROOTFILE}"
    sed "4iexit 1" -i "${CHROOTFILE}"
    sed "5ielse" -i "${CHROOTFILE}"
    sed "\$afi" -i "${CHROOTFILE}"
    if cat "${CHROOTFILE}" | sudo /usr/sbin/chroot "${target}" /usr/bin/env -i   \
            HOME=/root                      \
            TERM="$TERM"                    \
            debian_chroot=" ${target} "           \
            PS1='(${target} chroot) \u:\w\$ '     \
            PATH=/usr/bin:/usr/sbin         \
            /bin/bash 
    then
        echo "command succeed"
        return 0
    else
        return 1
    fi
}

usage()
{
    echo "Prepare an valid chroot environment"
    echo "$ mount_chroot.sh target [filename]"
    echo "Examples:"
    echo "$ bash mount_chroot.sh /mnt/sid"
    echo "$ bash mount_chroot.sh /mnt/sid myscript.sh"
    exit 0
}

main()
{
    nbargs=$#

    if [[ ${nbargs} -ge 1 ]]
    then
        target=$1
    else
        echo "--- Give at least target as argument"
        usage
    fi

    echo "--- chroot target is ${target}"

    if [ ! -d "${target}" ]
    then
        echo "--- Error: not a directory"
        exit 1
    fi

    if [[ ! "${target}" =~ ^/mnt/ ]]
    then
        echo "--- Error: not mounted under /mnt"
        exit 1
    fi

    if ! ask_for_execution
    then
        echo "--- Give the good target"
        exit 1
    fi

    if ! check_virtual_kernel_filesystems
    then
        if ! mount_virtual_kernel_filesystem
        then
            echo "Mount failure. Please fix it!"
            exit 1
        fi
        if ! check_virtual_kernel_filesystems
        then
            echo "Mount failure. Please fix it!"
            exit 1
        fi
    fi

    if [[ ${nbargs} -eq 1 ]]
    then
        bash ~/target_chroot.sh
    elif [[ ${nbargs} -ge 2 ]]
    then
        shift
        script="$*"
        echo "--- script is ${script}"
        target_chroot "${script}"
    fi

}

if [[ "${BASH_SOURCE[0]}" == "$0" ]]
then
    main "$@"
fi